Boost vs N/A - questions
 

This has been covered in many threads, but I have specific questions that I have not found by searching. So here goes. No flaming plz.

Boosting has obvious benefits in power, but the FA20 engine seems prone to issues when boosting—too much anyway.

My question… is it more reliable to focus on N/A gains? There appears to be a lot of mods that can be done to provide reasonable gains. Would it be more stable?

I've read that the "built" engines, unless by extremely reputable shops are often unreliable, however I am curious about DDs not track cars for the purpose of this thread.

For almost the same $$ as boosting, if you did headers, power blocks, throttle control or OFT, and the like couldn't you have solid gains and a measure of reliability?

This is vague, open-ended, and probably naive, but I wanted to get some real info in one thread. Again, flaming me does not add to the conversation. I'm fairly new to the car and learning as I go. So…

Better to boost or build up N/A power?Boost vs N/A - questions

Don't add boost unless you're ready to replace the engine potentially. Just get a tune for your car and see how you like it, it makes quite a difference.

Welcome to the group, there, allenframi - :clap:

For a DD, I'd suggest you just leave the engine alone.

;)

If you're not going to track, and stay strictly to DD, stay NA.
Items in bold you don't really need (Power blocks, throttle controllers).
Headers, E85, good set of tires, coilovers, and a good tune (OFT/ECUTek) is all you'll need.

Like others have mentioned, adding boost comes with risk, and is one you have to keep on the back of your mind always, in case your rods decide to play a rendition to "Knocking on heaven's door". There are measures you can take to mitigate it, like installing good supporting mods, but the risk is still there.

I think with mild boost the engine could be more reliable. I say that because at least in my case, when my car was NA, I would routinely rev it to redline to get any power. And always keep it above 4k rpm just to stay out of the dip. I would bounce of the rev limiter daily. I looked like a real douce. That all ended after I got my ESC. Granted it only gives me 5 lbs of boost, but I pretty much never go over 5k rpm because that's where I run out of torque. I've gone over 200,000 boosted miles and expect to go another 200,000.

NA gains top out pretty quick until you start spending bucket loads of money, and even then they start to become marginal pretty quick. You would be surprised how good a low boost setup will feel. Even 260whp is a huge difference. If you be reasonable about expectations, pick the proper supporting mods, and work with a tuner who knows the platform you will be fine.

The Subaru FA20D boxer in the twins has a 12.5:1 compression ratio.
That's quite a squeeze for any production engine that still runs reliably.
The FA20F that they put into a WRX is reduced to 10.6:1 before they try stuffing in more with the turbo.

Honda K20A in most commuter cars is 9.8:1 and only gets bounced up to 11.5:1 for the R cars with a lot of prosthetic appliances.

NA mods for this platform are pretty limited if you are chasing power so if you're happy with around 30whp higher than stock then NA is the way to go. I personally daily drive my boosted 86 and have been doing so for a year now. So far it's been pretty reliable as I only tuned it to around 8psi which makes around 290whp while keeping the stock injectors ,fuel pump and stock block. Reliability mods have only been an oil catch can and oil cooler. If you have some knowledge on proper maintenance or know someone that knows how to work on boosted 86s then you're probably fine to boost.

A mild tune with a supercharger might be fairly reliable. But stay NA and wind that car out. If you need more power get a different car.

Get a centrifugal style supercharger, it’ll keep the torque lower but the top end solid when you rev out. Can make about 260whp/200wtq easily and still be pretty reliable.

Welcome to the forums OP, as you see above there are lots of opinions.

My questions for you are, what are you looking to spend and what about the stock power delivery don't you like?

What is your end goal is the question back to you?

To answer boost, i have a Cosworth Supercharger on mine for 2+ yrs and its being used as a daily with no issues. It is only mild boost though, 0.5 Bar/ 7.25 PSI with regular pulley and no other supporting mods. As long as you dont chase crazy power numbers, which is the risk with adding boost, as you can always add a bit more boost and then a bit more again.... And thats where it all goes kaput. Cosworth's analysis suggested this to be about the safe level of Boost and I trust their research as a former F1 engine builder.